The scholars of Ahl al-Sunnah hold that the young children of the believers are in Paradise, and Allah honors the believers by joining their offspring to them there: 'And those who believed and whose descendants followed them in faith — We will join with them their descendants' (Quran 52:21). Every child is born upon the fitrah, the natural disposition toward Islam, before any influence changes it, as the Prophet ﷺ taught. Concerning the children of the disbelievers there is some difference of opinion, but the Prophet ﷺ answered the question about them by saying, 'Allah knows best what they would have done,' entrusting their affair to Allah's perfect justice and mercy. So a parent who loses a young child should have hope in Allah and patience, expecting reward.
Q&A · Death & Afterlife
What happens to children who die young — do they enter Paradise?
Evidence — the daleel
On deen2u
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.