The baby arrived and the older one changed: he regresses, begs to be held, acts «up» right when you're nursing, or says to give the little sibling back. Between the exhaustion and the guilt, you don't know how to hold them both.
Exhaustion and tenderness for the baby can turn the older one's jealousy into irritation («he's not a baby anymore, he should get it»). Stop. Jealousy isn't wickedness or a setback: it's the real pain of a child who fears losing his place. Acting «up» is his way of saying «do I still matter?». Reading it that way turns the reproach into a hug.
For the older child, a sibling's arrival is one of the biggest losses of his early life: he stops being the only one, sees the attention that was all his get divided, and has no words for the earthquake he feels. Regressions (talking like a baby again, asking for a bottle, wetting himself), defiant behavior right in the baby's moments, or saying «I don't want him» are normal expressions of that fear, not cruelty. What he needs isn't a lecture about being the older one, but the certainty that his place is still intact. The goal isn't for him to love the baby right away —that comes—, but that he not have to compete to know he still matters. Exclusive time, naming the feeling and giving him a role without forcing it usually unblock more than demanding maturity.
Don't scold him for the jealousy or demand he love the baby now: forced love takes longer. Don't use «you're big now» to ask him to give up his need for you. Don't compare him with the baby or dethrone him all at once from all his rituals. Don't let the regressions pass as manipulation —they're signals—. And don't unload your guilt by pressuring him to show he's «happy» with the sibling.
No ranking, on purpose: no two children are alike, and yours isn't even the same as yesterday. Read which one fits your home, today — or combine them.
Protect exclusive moments with the older one, even short ones, where he has all your attention without competing. Five minutes of full focus are worth more than a distracted hour. Feeling that his place still exists lowers the jealousy more than any speech about being a big brother.
Give words to what he can't say: «Sometimes it makes you angry that the baby takes so much of me, and it's okay to feel that.» Naming the jealousy without punishing it defuses it; denying it makes it grow. A child who can say «I'm jealous» needs less to act up to show it.
Offer him ways to take part that make him feel important —bringing the diaper, singing to the baby— without forcing him or turning him into your helper. If he wants to, he earns a valued place beside the baby; if he doesn't want to today, he isn't forced. The bond with the sibling grows when it's a choice, not a chore.
Prepare the older one before the birth when you can, but the real work is afterward, in the everyday. The baby's moments (nursing, getting him to sleep) are the ones of greatest risk for behavior: anticipate by giving the older one something of his own right then. If there's another adult parenting, split up so the older one isn't always left in the background. Be patient: love between siblings is built over months, not days.
Jealousy of a new sibling is normal and is almost always worked through at home with time and containment. It's worth consulting the pediatrician or a professional when the regression is intense and persists well beyond the first months; when there's real, dangerous aggression toward the baby that doesn't ease with supervision; when the older one falls into sustained sadness, marked anxiety or withdrawal; or when his distress doesn't improve despite exclusive time and containment. Telling the expectable jealousy from a reaction that settles in and won't ease is what points to whether support is needed. This is peer commentary, not clinical advice.
Everything in this house is peer commentary and suggestion — it does not replace professional help. It's every mother's and every father's responsibility to notice the situation and to seek it when it can serve. If you need a number, check the directory of helplines by country. The full disclaimer, here.