Raising rent if tenant's kids move in

[Jay Elvin]

Hi everyone, 

My tenant and his girl friend rent a 2 br unit at $975.  There lease is expiring in July and they plan to renew.  He informed me today, that due to circumstances with his ex-wife, his two young kids will be moving in.  Basically, his kids will share a room. 

This my first multifamily home so all these experiences are new to me.  My thought is that I should raise rent since I pay for both gas heat and utilities (water, sewer, trash).  The tenants pay for electric.  With 2 additional people living there, I assume these costs will go up. 

My question is: should I raise rent and by how much?  

My first reaction is to raise rent by $25-35 per month. 

I appreciate any advice.  Thank you. 

Jason