Relationship Help

My SO and I have been dating for 11 mths. His previous relationship lastest 6 years on and off. During that time his mother and siblings gain a relationship with ex g/f. Well, since we've been together they HATE me, Idk them personally and visa versa. They've tried EVERYTHING to break us up. Creating fake social media pages, fabricating stories abt me with other men ect. They see us together and they don't speak to me. I have don't nothing wrong to these ppl and since I'm pregnant they are throwing grenade making things extremely difficult. Asking him to choose between me and his family. I've wanted to give up so many times but we know the love we share and just won't walk away from each other. Any advice on how to handle this. I need help please