HELP!! is Net Cash Salary 2600€ enough for family of 3?

It should be ok for a family of 3.
I think you will get extra 90Eur for your kid monthly allowance.

I live with precise the same salary but we are 4 (my wife and 2 young kids 4 and 6 months old). The salary is enough to living, but no more then that. Buying a car is out-of-the-question. Buy groceries, or fish or meat in the main supermarkets chains like Carrefour is also (for me) out-of-the-question, since they are quite expensive. I need to go to the Arab markets where things are less expensive. Quality is then not so good.
Clothes and shoes are also quite expensive.

You may opt to live outside Brussels where renting is less expensive, but then you need to rely on public transportation (they work well) or buy a car (Brussels traffic is a nightmare)

Brussels is a nice place to live. But to live withouy counting every single cent. a family need 70.000,00 EUR/year before taxes.