While searching for information to expand my Sullivan line, I found your message, you may have the answer already since you posted this in 1999. I have been taking with a Pat Rowland Carothers on Facebook and she shared the following information:

William Sullivan born in 1760 and Joseph born in 1771. Daniel and Margaret were married in 1770, so I don't know if Daniel was married before Margaret, (Daniel was born in 1730, and Margaret was born in 1734), or if the records are wrong about William. According to family lore, my 2X Great Grandfather, John S. Sullivan, apparently "hated" his father and never talked about him, so no-one is sure of his name.

His full name is John Smith Sullivan, he is my 2nd cousin 6x removed.