I have both Marcus and Weiselberg names in my family tree. Here's the info:
Caroline Marcus married Jacob Farber, (I do not have birth/death dates or locations) and had the children:
Marcus Farber, b. 1860 in Lanzany, Lezany or Laczany, married Mary Schanzer, b. about 1863 in Lysowa. They immigrated to Buffalo, New York in about 1907.
Marcus and Mary had the children:
Natalia "Nettie" Farber
Natalia "Nettie" Farber married Harold Weiselberg, and they had the children Solomon Weiselberg and Harold Weiselberg.
If this sounds like your family, I'll be happy to trade info.