While Lincoln issued the proclamation, credit for making Thanksgiving a national holiday should go to Sarah Josepha Hale, the editor of Godey's Lady's Book, a popular magazine for women in 19th century America.
Family Medical Leave Act (FMLA) Overview The Family and Medical Leave Act of 1993 (FMLA) provides covered employees with an entitlement to a total of up to 12 weeks of unpaid leave (LWOP) during any 12 month period for certain family and medical needs.
Your company is correct. FMLA is for the care of immediate family which is defined as child, parent, sibling. It does not allow for aunts, uncles, grandparents, cousins etc. The DOL website specifically states that FMLA for grandparents falls under the employer's leave policy but is not covered by FMLA protection.