Is or was baptism a part of Judaism? My aunt is looking into our family history, and apparently we have family who are Jewish, but may have records of infant baptism.
Is there any chance it was a way to cover Judaism? Is it absolutely forbidden?
Baptism has never been a part of formal Jewish practices. In the 1st century, some fringe groups did do baptisms but it was never adopted by the mainstream.
The family might have converted to Christianity and that is why you have the records.
Were your Jewish ancestors of Sephardic origin? They may have been what are referred to as "Crypto Jews" i.e. Jews who pretended to convert to Christianity under pressure or threat, but who secretly retained their Jewish identity and faith.