ISO half siblings

Hey there I am searching for my mother-in-law's half siblings. Sometime between 1966 and 1970 (we believe 1967) her father met a woman in Washburn, Wisconsin. She bore him twin. We believe they are girl/boy twins. We don't know if his name was ever on their birth certificate but his siblings did confirm that they were definitely his children. All we know of them is that they were given up for adoption by their mother. I don't know how their father felt about this as he died in 1991 and I don't know that she even knew of them until after he died. If anyone knows anything, please email me: caro-nm@hotmail.com These two people have four half siblings, all of whom have their own families. I cannot say for the others, as I have not spoken with them about this, but I do know that my mother-in-law, one of their half siblings, does want to to know them and meet them and have a relationship with them. We have been working on our genealogy for quite some time and would love to find these two people. We have much information to share, many family stories and family photos. Please know that we are looking for you and we do want to find you. We know you probably have a great adopted family and we have no intention of weaken that relationship at all. We just want to know you and want you know your other family. But most of all, we just want to know that you are happy and are having a great life. Thank you for anything and everything you can do to help. It is greatly appreciated!!