How can my boyfriend get custody of his kids?

my bf kids mother has been running the streets all summer and now shee is not tryna come pick up the kids. she does this every summer, the agreement is to get them every weekend. so now she say's that the kids cant come home because its bed bugs all over ther house its been a month now and the are suppose to be still in the house. school is about to start in about 2 weeks and she hasn't called yet wit any information. so my boyfriend just wanna get the kids permanatly and take care of them his self.