Do you think its weird of him to come back to USA without marrying her?

My friends son is in Philippines for 9 mos now with his girlfriend. And his father said he won't commit like he's scared of commitment because he knows him. She not his second Asian eithet he dated Thai, Chinese and another Filipina. And his son is complaining how hot it is in Philippines. So my friend said his son is coming back to USA in December. I thought its weird because his son is basically living with his girlfriend in same roof for like 9 mos and suddenly coming back to USA without asking to marry her. I asked him asked his son the reason if he come back. Im not sure if they already had sex but since they were living in same roof maybe they already did. by the way his son doesn't have a job either and only rely on US government assistance.
Do you think he will marry her? Or change his mind again?
Do you think its weird of him to come back to USA without marrying her?
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