How many SNPs are needed to perform haplotype analysis on siblings and their mother?

Question

[Joel Wallenius]

Hello,

I'm hoping to get SNP array data from a handful of siblings as well as their mother (father is gone, sadly), to ultimately get phased genotypes/haplotypes of one of the siblings to see where a particular SNV in this specific sibling might have come from, and whether it's significant or inconsequential.

I know this can be done with STRs/microsatellites, as they are highly polymorphic. But is it possible with SNPs? How many SNPs are there in a 1Mbp window? Enough to tell siblings apart from each other? From their mother?

Please excuse my ignorance, this is my first time asking these types of questions.

Thank you!