If your boyfriend is an illegal here and he is on probation and now detained by immigration, then he is going to most likely be deported. It makes no difference if you are a citizen because you are not his spouse and his daughter doesn't have the age of majority to I believe sponsor him here. You need to talk to an immigration attorney and see if you are able to and willing to get married if you are intending to stay with him, then marriage may prohibit his deportation. However, if he is being prepared for deportation for a criminal act (of which he is on probation), federal law may actually prohibit the marriage if it may be viewed as a way to obstruct justice. Again, you need to talk to and he needs to talk to an immigration attorney to know what options (if any) he may have.