Single parents

I’m noticing, especially in this newest season that a lot of the cast comes from single parent households, and only single mom households. Logan, Dylan, Abbey, etc. I understand this is common, but in my personal life I realized a lot of people I know with special needs also have single moms. I’m super curious to know if any studies have been done around whether it is more likely that adults/kids will have a single mom if they also have special needs. Would love to know others’ thoughts too