Help! My fiancee wants his family to move in with us

Hello Miss Petite, I am so pained right now. I've been dating my fiancee for 5 years before he proposed last year. He wasn't from a rich home neither am I.After being jobless for 2years he got a good job and we were able to move from a one bedroom BQ to a 3 bedroom apartment. However, I noticed he just keeps spending all his money on his family.He bought a car for his mum and I still use public transport to work.He spends so much on his 3 younger sisters
Though I am an orphan, I have just one sister and she is married so I don't really have obligations.
Last week, we were discussing about the wedding in March when he said, he wants his family to move in with us. I was shocked because for a new marriage, having family members around isn't a good idea . I told him it's better to rent a house for them.He says his mum has been lonely since his dad died and as the only boy he wants her to be near him .His dad died four years ago
 To make matters worse, he said his three younger sisters would also stay with us so they can take care of her.
When I tried to tell him I won't feel free,he said if I love him, I would love his family.He said there is no going back and since we have three rooms it's convenient. He always says his mum sacrificed for him and it's time for her to enjoy
Is this a bad sign? How can I start married life with in laws allover? Please advice 

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