I founded a startup(solely owned) after my marriage and am in process of cofounding another one with a friend of mine. I am in middle of a possible separation or divorce with my spouse. It definitely drains you and impacts abilities to focus on startup. Is it possible to avoid my spouse claim any share on the startup? Can it impact the new startup I am planning to co-found soon?
This is a good question and an important consideration for your current company and any future companies you start. While there can certainly be exceptions, in my experience, if you acquire or create a new asset (including a company) while you're married, it is generally considered a marital asset and subject to division during the divorce process.
I'm not an attorney, so you should ultimately seek a legal opinion on this, but if a separation or divorce is imminent, you may want to wait until after your divorce is final before embarking on your new startup if you want to avoid having it pulled into the divorce negotiations.
If you would like to discuss this further, let me know.