Is this lengthy sentence grammatically correct?
Is the following sentence grammatically correct? (There are lots of complex and compound clauses combining in one sentence. Is it still correct grammatically?)
"I will be very happy if I come to your house next week, but I can’t go because I have to look after brother’s son."

Question

Answer

"I would be very happy if I could come to your house next week, but I can’t go because I have to look after my brother’s son."

Answer

"I will be very happy if I come to your house next week, but I can’t go/COME because I have to look after MY brother’s son."

Answer

"I would be very happy if I could come/go to your house next week,  but I can’t (go/come) because I have to look after my brother’s son."  
This is a hypothetical impossible situation. so both  "will and "can" in the 1st clause must  be in modal form. The 2nd go/come is optional.