The familial change would actually be covered by fair housing legislation, though even if it weren't I would still allow the addition as a normal change in life circumstance.  

So there is no way to say for sure, especially in light of Government legislative help that might come along.Just my 2 Cents.

Connecticut recently passed legislation that allows “Accessory Dwelling Units” sometimes referred to as Auxiliary Apartments.  

This is a huge expansion of what this legislation has traditionally called for.

Could legislation come down the pipeline that makes OOS investors have a harder time? 

What we are seeing here in Massachusetts is consistent efforts to pass legislation like 2% real estate transfer tax, tenants right of first refusal, some sort of rent control, a form of eviction moratoria etc.

It's interesting how investors are basing the prices they will pay for properties on STR rental rates instead of LTR rates.With the changing legislative and tax situations for STRs, there are bound to be some that experience big losses with this strategy.May be prudent to buy deals based upon prices that break-even with LTR rates and recognize STR income as a "bonus" for as long as it lasts.

@Kyle Gendron Great point about Albany being the capital - legislators come from around the state with their aids who often need an inexpensive place to stay. 

I'm getting into the STR game and future legislation is a big concern.

I know that in the state of VA these have closed because of legislation that passed regarding the fairness of these loans.