Hi mama! From what I know, marami sa mga babies ay may underbite pa around that age kasi the jaw is still developing, pero honestly best to check with the pediatrician or a pediatric dentist para ma-assess ng professional kung normal lang ito or kailangan na mag-monitor, one of my mum friends had the same concern with her son at sinabi ng dentist niya na kailangan lang i-observe, pero bawat baby is different talaga so better safe than sorry!