The people closest to you — parents, siblings, grandparents, and the rest.

• mammotherfeminine; informal/everyday word
• tadfathermasculine; soft-mutates to 'dad' (e.g. ei dad = his father), nasal-mutates to 'nhad' (fy nhad = my father)
• chwaersisterfeminine; plural 'chwiorydd'
• brawdbrothermasculine; plural 'brodyr'
• mam-gugrandmotherSouth Wales term; North Wales uses 'nain'
• naingrandmotherNorth Wales term; South Wales uses 'mam-gu'
• tad-cugrandfatherSouth Wales term; North Wales uses 'taid'
• taidgrandfatherNorth Wales term; South Wales uses 'tad-cu'
• merchdaughterfeminine; also means 'girl/woman'
• mabsonmasculine; plural 'meibion'
• modrybauntfeminine; both maternal and paternal
• ewythrunclemasculine; informal 'wncwl' also common
• teulufamilymasculine; 'fy nheulu' = my family
• rhieniparentsplural of 'rhiant' (parent)
• brawd neu chwaersiblinglit. 'brother or sister'; Welsh has no single native word. Plural 'brodyr a chwiorydd'. Modern coinage 'brawdchwaer' exists but is rare
• cefndercousin (male)masculine; a male cousin specifically
• cyfnithercousin (female)feminine; a female cousin specifically
• babibabymasculine; everyday word, also 'baban' (more formal)
• gŵrhusbandmasculine; also means 'man'. 'fy ngŵr' = my husband
• gwraigwifefeminine; also means 'woman'. 'fy ngwraig' = my wife