What is a marriage?  A contract.  You do not necessarily think about the legal ramifications at the wedding, but who inherits the house if one of you dies, or who gets the house in the case of a divorce?  You can fix that with a prenuptial agreement, you can fix the contract.    However, just because it is a contract does not mean it is enforceable.  Talk to an attorney and figure out how to make it enforceable.

Getting married can change your life.  It can also change how you hold property title.  So you and your boyfriend bought a house together and took title as Tenants in Common.  The only unity there is the Unity of Possession.  Either one of you can sell your interest in the house without notice to the other owner.  But if you get married, neither of you can break the tenancy nor otherwise convey the property without consent of the spouse.

Married couples hold title as Tenants by Entirety.  This includes the unities of Joint Tenancy with Rights of Survivorship plus the Unity of Marriage, which subscribes to the legal fiction that a married couple is one entity.  You cannot disinherit your spouse.  Your wife or husband is entitled to your homestead property when at death you do part (unless there is a properly executed marital agreement).

Even if you made a will before you got married, your spouse is still entitled to half your estate, the same as if you had died without a will.

What if you want your children from a previous marriage to inherit the house without having to share it with a stepparent?

Again, talk to an attorney to fix the contract and to make it enforceable.  Or pick your mate right and be willing to forgive…or be really lucky like I am.