Why is my 13-year old male cat acting bad since the birth of my daughter?

Your kitty isn’t adjusting well to the new member of your family and he feels he is being replaced. He is just concerned why this creature has taken over his territory. Take about 30 minutes out of your day to socialize with him, give him individualized attention to let him know that he isn’t being replaced and that you still love him. Hold him, cuddle him and give him treats. Your kitty seems to feel jealousy but getting some cat toys and playing with him a bit will make it better. If you feel comfortable, play with him and include your daughter so that they can bond and he won’t be so afraid of her.