All the children of the woman who breastfed you, from all of her husbands, are brothers and sisters to you
Question

                I was breastfed by a woman along with one of her sons, then her husband died and after she completed the ‘iddah she married another man and had children with him. Are her sons from the second man also brothers to me?.
Praise be to Allah.
    If the situation is as described in the 
    question, and you were breastfed by her for five complete feedings or more 
    within the first two years of your life, then her children from the first 
    husband are your brothers through your father and mother through 
    breastfeeding, and her children from her second husband are your brothers 
    through your mother through breastfeeding only, because Allah said in Soorat 
    al-Nisa’, when mentioning the women who are haraam for marriage 
    (interpretation of the meaning): “Forbidden to you (for marriage) are: 
    your mothers, your daughters”; then He said after that: “your foster mothers who gave you suck, your foster milk suckling sisters” [al-Nisa’ 4:23]. And because the Prophet (blessings and peace of Allah be upon him) said: “What becomes mahram (forbidden for marriage) through breastfeeding is that which becomes mahram through blood ties.” Saheeh – agreed upon. End quote.