EconProf from this link http://www.wimer.net/landlord/a/landlords_rights.pdf it states
“Also, you cannot evict you
while the lease is in effect, except for reasons
such as your damaging the property or failing to
pay rent. A lease gives you and the tenant the security of a
long-term agreement at a known rent.
The disadvantage of a lease is that if the tenant
ends up being undersirable, but complies with
the terms of the lease you must ride out the term.”
I believe marriage is a protected category as far as discrimination goes, so if you want to risk a lawsuit evict away.
My personal take would be if he spends less than half the nights there he is not a tenant.