I would like to know if my visa will be approved by Germany embassy if I apply to live with my husband his 2 parents and his little brother. The house is 100m square.2 toilets 3 rooms 1 kitchen and bathroom 1 sitting room
Well that was a struggle! I eventually found:
“Without prejudice to state provisions, sufficient living space is usually deemed to be available if 12 sqm of living space are available to each family member aged above six and 10 sqm of living space for each family member aged below six. Adequate availability of the facilities (kitchen, bathrooms, lavatories) must be ensured. A shortfall of about ten per cent is acceptable” (2.4.2. General Administrative Regulation to the Residence Act).
That is a quote from this PDF on the BAMF (Bundesamt für Migration und Flüchtlinge) website.
There will be a total of five of you, so with a 100 sqm house you will have 20 sqm each. The only possible catch is what "100 sqm" means. The space within an apartment counts fully, but cellars don't, and outside balconies count 25% etc. See this answer for more details. However it is unlikely that will bring you under the 12 sqm figure; also, if you got the 100sqm from the property details (rather than your husband getting out a tape measure), they will already have done any necessary pro-rating.