No it doesn’t, there is nowhere near enough information for you to make the assertion that OP has a better chance of keeping (most of) the house based only on the fact her ex has an inheritance. What you have written presumes the inheritance will be taken into consideration from the beginning - it won’t.
You also have to keep in mind that it’s not just the house to be considered but also all savings, debt, pensions, earnings, earning potential, mortgage capacity, length of marriage, child residency etc.
The starting point will be to disregard the inheritance & divide the marital assets in a way that provides for everyone’s needs, not wants. Only if there is not enough to do that, will the inheritance be considered.
So for example, OP says they have a child & let’s hypothetically say the family home is a 3 bed house now but the court decides a 2 bed flat each will meet everyone’s needs adequately.
Scenario 1:
There is enough in the marital pot to provide them both with a good deposit & they both have equal capacity to raise the rest through a mortgage then the assets will be divided 50/50.
Both get enough to finance a 2 bed flat from the marital pot.
Inheritance is not included.
Scenario 2:
OP earns significantly less than her ex so has a lower mortgage capacity therefore assets will be divided in her favour.
Both get enough to finance a 2 bed flat from the marital pot.
Inheritance is not included.
Scenario 3:
OP earns significantly more than her ex so has a higher mortgage capacity therefore assets will divided in his favour.
Both get enough to finance a 2 bed flat from the marital pot.
Inheritance is not included.
Scenario 4:
There is not enough in the marital pot to provide them both with a 2 bed flat each therefore the inheritance will be included. So OP taking all the marital assets & her ex being told to use his inheritance to house himself or the OP even getting some of his inheritance on top of the marital assets.
The above is a very simplistic view & doesn’t taken into account several key factor but hopefully you get the gist of what I’m trying to say.
Obviously if one of them is an extremely high earner or he inherited millions (which I doubt as he’s waiting for his sister to buy him out) then the outcome may be different.