Complex sentence: Eva and Franklin have a second child, Celia, who is lively and cheerful, but her birth does nothing to lessen the tension within the family as Kevin immediately shows disdain and jealousy towards her.
Split into simpler sentences: Eva and Franklin have a second child, Celia, who is lively and cheerful. However, her birth does nothing to lessen the tension within the family, as Kevin immediately shows disdain and jealousy towards her.