awkward position. in yesterday's world, not a problem.
in today's world, you have to be careful.
you are smart to ask about this.

i would feel better about it if he's been married and had
kids of his own. go with your gut feeling. if anything
feels strange, don't be afraid to ask. like others have
stated, let others know where you are.

anyways, i wouldn't have too much expectation
as far as professional psychotherapy sessions go
but you may learn valuable things from him
in other ways. it's up to you to make the most of your
resources.