It does not matter who the father is.
If the woman takes care of the kids, there is no abuse.
It is her work. Children need someone to take care of them.
Preferably their mother.
She does her job.
You do your job.
You both pay rent.
Be happy and content.
Smile when you confront her in the staircase. Be friendly.
Ask her to come and see your flat. Give her coffee and bisquits.
Be a Mensch.