Complex sentence: She is the eldest of three children born to Michael and Carole Middleton, a former flight dispatcher and flight attendant, who in 1987 founded Party Pieces, a mail order private company that sells party supplies and decorations with an estimated worth of £30 million.
Split into simpler sentences: She is the eldest of three children born to Michael and Carole Middleton, a former flight dispatcher and flight attendant. In 1987, Carole and Michael founded Party Pieces, a mail order private company that sells party supplies and decorations with an estimated worth of £30 million.