Not my situation, just posting here for traffic, rather than the Pregnancy board, in the hope of some getting some answers because Google isn't being very helpful.
Couple with young baby; baby was unplanned. They live in her mortgaged house, he pays no rent and isn't on the deeds. He has done some DIY. He only works occasionally, contributes nothing to the household, smokes and takes drugs. She told him she the relationship is over and that she wants him to leave. He ignored her, so she followed the standard advice to give him notice in writing; he tore up the letter and laughed in her face. He acts as if he's the man of the house with every right to be there. She's planning to change the locks soon.
However, for all that, she's discovered she's pregnant again. She wants to keep the baby, but still wants to end the relationship - soon, before her pregnancy is obvious. Although he has PR for the elder child, she intends to tell him the baby she's carrying isn't his. I'm not sure if her plan will work. Will he be able to demand a DNA test to prove paternity?
Appearances matter to him, and while he likes the "status" of being a father, he's not hands-on, has never actually bought anything for child who's already here, and CMS will be virtually non-existent. Hence her reason for wanting to exclude him.