If I identify with any specific branch of Christianity more then the others it's The Baptists (but with some Quaker characteristics), especially The General Baptists. But one annoyance I have with a lot of modern Credo-Baptist sects is a refusal to state a clear absolute minimum age one can choose to be Baptized, with some even thinking Elementary School kids can be old enough.
Baptism should be viewed as in part a Commitment. So anyone you consider to young to get Married is also to young to be Baptized because I view Baptism as in-part becoming Betrothed to Christ. But I think most Churches are permitting Marriage at too young an age as well.
Exodus 30:14, Leviticus 27:3 and Numbers 26:2-4 tell us that about 20 is when The Torah considered someone legally an Adult Citizen of the Congregation. Numbers 1:3 and 2 Chronicles 25:5 also say 20 is the minimum age you could serve in the Military.
However since I view New Testament water Baptism as evolving out of the Water Immersion ritual that was part of consecrating the Aaronic Priesthood (Exodus 29:4, 40:12 and Leviticus 8:6) applied to the Priesthood of All believers Doctrine that only Congregational Polity practicing Christians even pretend to take seriously. Age milestones related to the Levites specifically may be worth looking at.
In Numbers 8:24 the age of 25 is when Levites start waiting upon the service of the Congregation, but in Numbers 4:3-47 the age of 30 is when they started to do the work of the Congregation.
One of the arguments against Infant Baptism being the original norm of the Church is the clear evidence that early Christian Tradition going back to at least the 2nd Century said 5 years of Catechism was necessary before Baptism This tradition remains formally in-place after Infant Baptism was standardized but is applied only to adult converts. But that combination makes no sense, why can Infants be Baptized right away but adults need to be prepared to know what they are committing to?
Now a lot of people in Acts seem to be Baptized right after they convert, but in Acts 2 and 8 we are dealing with people coming from an Israelite background, the Ethiopian Eunuch was reading Isaiah already, the stuff the 5 year Catechism was necessary for may be stuff they already knew.
I'm a true Paulian Christian, I don't believe we are under The Law in any rigid or legalistic sense. But I am Hebrew Roots enough to still believe The Torah is useful, for things like this especially. And I think a lot of early Christian traditions that don't seem directly mandated by The New Testament have their roots in applying Torah ideas though a New Testament filter.
So I think either 25 was originally the Minimum age to begin Catechism and then 30 when 5 years have passed for Baptism, or Catechism could begin at 20 with 25 for Baptism and another five years before you can be considered an "Elder". I don't think NT use of Presbyter meant Elder or Senior in the old age sense but more closer in application to the Japanese honorific Sempai, I think Congregational polity denominations often cede to much ground to Presbyterians and Episcopalians on how to define those words.
It is of course possible the Catechism was only required for Adult Converts and those raised in the faith were expected to know when they reached the minimum age. But I do think it'd a mistake for parents to pressure their kids to hard to get Baptized as soon as they turn 20 or even 25, let them think about it for awhile if they want to.
Thirty as an ideal age for Baptism is a natural conclusion one could draw from Luke 3:21-23 seeming to say Thirty was when Jesus was Baptized.
So 20 as the minimum age for even beginning to prepare for Baptism in my view should also be the minimum age of Consent for Sex and Marriage. But I can even sympathize with raising that to 25 based on the science about how the Brian isn't fully developed till 25.
Rabbinic Judaism at some point developed the Bar Mitsvah tradition of considering adulthood to in some sense begin at 12 or 13. I don't know where this came from, there is nothing supporting it in The Torah or anywhere else in The Hebrew Bible. Manasseh became king at 12, but he didn't turn out to be a very good King, maybe that had something to do with it.
However a lot of Christians think 12 as some sort of milestone age is vindicated in The New Testament by Luke 2:40-42. Nothing here says Jesus being 12 is the reason for anything. The Torah required only adult males to attend the Pilgrimage Festivals but those Men did often bring their families including Wives and Children. Nothing in Luke 2 says Jesus wasn't there for prior observances of Passover, this is just a time when something notable happened. And it's notable precisely because it's unusual for someone this young to be this intellectually skilled. This is a story about how Jesus as the Son of God was not like other 12 year olds, it's not a model for anything.
[I've also been considering a theory on New Testament chronology that have the Passover when Jesus was Twelve be the first one after the removal of Archelaus which makes sense as the first time Joseph would have brought his family given what the end of Matthew 2 says. But that's a secondary theory and not necessary to explain it.]
Contrary to popular assumption NO it was not in Ancient or Medieval times common for people to get married with at least the woman being as young as 16 or even 12 in some claims. While on the books marriages that young might have been technically allowed all the evidence shows that in practice the norm was usually at least 20. The notable exceptions were usually among the Aristocratic or Royal Families making important marriage alliances and even they often weren't consummated right away. But those exceptions are often what people write historical fiction about helping spread the confusion.
There are no Biblical verses stating a clear ideal or minimum marriage age, but at least 3 notable people didn't get married till 40, Isaac, Esau and Moses (Jacob was Esau's twin and he got married even later).
And no nothing in Scripture supports the "if she can bleed she can breed" meme people assume about pre-modern cultures.
The one Bible verse some will cite for that is 1 Corinthians 7:36 but it does not explain what "flower of her age" means, the natural assumption to me is Puberty being over not when it starts, that "flowering' is a process not a singe event. "Flower" isn't even a good translation of the Greek, the Greek text here is communicating the idea of being physically fully grown, which happens at about 20. So I would consider 20 the age of consent for sex but still hold off on marriage till 25.
Also regardless of age some people abuse "let him do what he will" from this chapter to defend martial rape. The context of this chapter is addressing believers questioning whether Sex and Marriage is right for them at all, Paul is giving people permission to enter consensual marriage, not disregarding the woman's consent.
Thing is I do want to lower the Voting Age, and some people may find that bizarre in the above context. But to me the whole point of Democracy is to empower the most vulnerable. The youngest people are the ones thinking about the future most which is why they need a greater voice. You aren't consenting to anything when you Vote, you are telling the State or Society what you prefer and they consent only if enough people agree.
But I do think 25 or 30 should be the minimum age to actually old office. I disagree with 35 being required for the Senate and Presidency, that should be lowered to 30 the age David was crowned at.
In both Numbers 4:3-47 and Numbers 8:25 the age of Fifty is when Levites retire. And looking at a lot of contemporary issues not letting people over Fifty stay in Congress sounds like a good idea. Letting people between 50-60 remain in advisory positions with no direct powers could also work. Sixty as a milestone age comes from Leviticus 27:3-7.
Thing about the Voting Age is you can't have it both ways, if you want to have a minimum voting age there should also be a maximum one because the elderly do at a certain point become functionally children again. Except that Old people vote the most Conservatively because they're most motivated by Nostalgia, so political bias clearly influences what Conservatives and Centrists think about the voting age since it suits their interests to stifle calls for radical change. So in my opinion either both the youngest and oldest can vote, or neither.