[texas dog lover]

A friend with two shitzu mix males, 5 yrs old, just recently took in a pregnant friend (she is having a boy) with a 5 yr old male child. Her alpha dog has started to growl and be aggressive to the boy. He is also urinating all over the house and marks his territory right in front of her friend. He is also very aggressive to her other dog, to the point of vicious fighting. Help! What does she do?

[german sheep]

The dog is totally overstrained because of the whole changed situation.
Nothing is the same, and the dog is overstressed to show that every little thing belonges to him and is fully under his controll.

To compensate this stress for himself, he has no other choice than to attack the other dog, because he is too frightened to push it on humans. (displacement activity)
If the situation does not change there will be the risk that, sooner or later, the boy will be bitten by the difficult dog.

But there must have been clear behavioural issues from this little dog in the run up to the existing situation.