My bio father quit claimed a house to myself and 2 of my siblings. The deed clearly states that we are "joint tenants and not tenants in common" . Sibling #1 has lived in the house since 2006. Sibling #2 moved in a short time later. Now here's the problem. Sibling #1 passed away in Jan. 08 Her spouse is still living there. We the survivors want to sell the house and have a buyer,I just don't know if I need to evict the in-law or not? I served him with a 30 day notice. I know in Illinois you have to follow the eviction process,but does that apply here? Thanks in advance

I am assuming that the house is in IL. Here is a link to the rules of being evicted. It is written from the evicties point of view but it will work for you. The rules still apply even with him being related.
Eviction
Good luck. Did he take her third of the house when she died? If so he is part owner and could buy the 2/3 from you two.

You have to go thru your state rules on eviction.

Was it joint tennants with right of survivialship, there is a difference.
Did their share of the home go to the other remainding owners at death,

I think that you should got through the eviction process in your state if you and your siblings already have a buyer for the home?