That is a tough one. I know here in the US, they say to avoid wheat until age 1, BUT all the teething biscuits, puffs, etc. that are made for babies, have wheat in them.
Celiac is hard to dignose also. You could give him wheat and symptoms may not appear until later. He could just get eczema from it or some other odd symptoms. He may not get the digestion upset.
If it were me, I think I would wait until at least a year, not only because you have a family member with celiac, but also wheat can be a high allergenic food.
Would your lo take homemade purees?
Also, not sure if you can get it done where you are, but I think there is a blood test that you can get done to see if your lo has the celiac gene. If he/she does, that does not mean that they will get celiac, but are at a greater risk.
Hope this helps, Wendy