Tenant strongly wants their family to rent my newly vacant unit

[Paul Brady]

I have a 2 family in central Massachusetts. My first floor tenants (who after a year have been great tenants so far) are strongly urging me to let their family move into the newly vacant 2nd floor unit. I have many people interested in the unit already. My question is has anybody dealt with having multiple family members/friends in the different units of the same property? If so how has it worked out and is it something that should be avoided for any reason ?