Complex sentence: In 1835, he married Margret Keyes Backenstoe, a widow with two daughters, a baby and an elder daughter, Virginia Elizabeth Backenstone, whom Reed did not adopt, but who nonetheless went by the name Virginia Reed.
Split into simpler sentences: In 1835, he married Margret Keyes Backenstoe, a widow with a baby daughter. Reed never formally adopted Margret Reed's eldest daughter, Virginia Elizabeth Backenstoe, but she went by the name Virginia Reed.