Aiyoh, I understand how difficult this situation is, especially when both your husband and in-laws agree! Most health authorities actually recommend waiting until 6 months before starting solids, and a few of us mums in my circle waited that long without any issues, baby akan cukup nutrients from milk alone pa. Maybe sit down with your husband and ask him specifically which paediatrician or guideline he's following, because most of the major ones (WHO, Malaysian Paediatric Association) suggest closer to 6 months when baby can sit up properly and show signs of readiness, not just age. It might help if you both refer to the same source together, sometimes our partners respond better to written guidelines than just mum-talk! Honestly, a quick check with a paediatrician you both trust might settle this and show your husband and in-laws a professional opinion.