Family Titles

Factual Questions
1

I understand second and third cousins…that’s not the problem.

So - Jane marries Adam. They have a kid, Sam.
A few years later, Jane and Adam divorce. And Jane meets and marries Bob. Jane and Bob have a kid, Tom.

Now, Bob and Sam would be step-father and step-son. But what are Adam and Tom? Are they “ex-wife’s son/mother’s ex-husband” or is there another, more common way to refer to that relationship?

2

Adam and Tom don’t have a familial relation to each other.

3

Adam and Tom (or Bob and Sam, even) could call each other “my son’s half-brother/my brother’s dad” which makes it seem a bit more family-oriented. This works, provided the sons are close. If they weren’t close, it would probably be as the OP described.