The Foster Dad by Christopher X. Sullivan

Chris and Mark are thankful to have Alex living in their apartment, but now they must adjust to each other.
Despite Chris’ reluctance to introduce the kid to family and friends, it’s impossible to keep Alex to themselves. Everyone is charmed by the precocious Alex.

Mark and Chris are committed to caring for this child, so when Alex speaks the last name of his grandmother, Chris is determined to keep it a secret from Child Services. However, from that moment on, there’s a countdown clock and Alex will inevitably be taken to his biological relatives.
When that clock strikes zero, Chris knows it’s going to be a very, very bad day. But for now they have Alex, and the three of them pretending to be a family is like a dream.

[The Foster Dad is the eighth book in the nine-book series, It’s Just Us Here. This 80,000 word installment continues the storylines of the final trilogy, Family and Fatherhood.]