S.G.
Hi B.,
The current thinking is that waiting until 6 mos to start solids is safest. Research is indicating that starting solids sooner may increase a child's chances of having food allergies because before 6 mos the digestive system is not mature enough to handle solid food. Ultimately, the pediatrician should be able to give you good advice for your grandchild - maybe his system is maturing faster than average and he's ready now...
Best,
S.