Mortgaging with less than avg credit?

Hello. I would like some professional opinion on a scenario. We just bought a house our selves and it went quite smoothly for our first hometime buying.

My sister and her fiance are looking to also buy a home as well. She has good credit at 729 and he not so great at 599. He makes roughly 80k a year and she makes about 30k a year. Can they still get a mortgage on a home around 349k? They need over $15,000 to put down and currently only have half of that. Is there any instituitions that can over look certain things even if it meant higher interest? At the end of the day they are able to afford $1500 month before utilities. If it matters, The home is in Ontario,Canada. My situation was easy as we sold off some of our stuff for our downpayment and our credit was good and I dont know what to recommend to her before she goes to the bank or lender.

Thanks!

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