Germany and family reunion

This topic about german embassy in Bangkok and visa to Germany issues.
At the first, some  introductory:
I’m Russian who live in Thailand with my family, wife and two children, they are Thai’s .
Not long time ago I was given national D visa, for IT work, in German embassy in Bangkok. 
I has applied alone and had intends to bring family later but I’ve read that is much more difficult than apply together im Embassy.
On web site page for family reunion has requirement for legalized Thai documents. I had given documents for legalization (birth certificate and marriage certificate ) but it will take about 6-8 weeks.
Now I realized I forgot to ask in embassy, if I still here, can they apply for visa without this legalization process or it’s required anyway.
So this is a question, if anyone know.: If we’ll come to embassy all together and apply for family reunion, legalization process is required or no?

Thanks for any suggestion!