Yes, Ida married Alois Gross first, then my ggrandfather. If Alois Gros was their father, wouldn't the boys have his surname after Ida married him? Also, in the attachment there is no notation above their names although there is above the names Jozef and Franz.
After this, Ida went on to marry a Weber and a Grohotolsky. To my count, I see 4 marriages in her life. So, the idea she has 2 more children is possible as well as her trying to make ends meet for her 2 Tanzos boys by marrying again. And again... What do you think?