10 Indeed, even in the absence of such express incorporation, the well-established rule has been that federal law affords recognition to familial status determinations as governed by the law of the relevant State. As the Supreme Court recognized in DeSylva v. Ballentine, 351 U.S. 570, 580 (1956), “[t]he scope of a federal right is, of course, a federal question, but that does not mean that its content is not to be determined by state, rather than federal law. . . . This is especially true when a statute deals with a familial relationship; there is no federal law of domestic relations, which is primarily a matter 9 See also Lee v. Comm’r of Internal Revenue, 64 T.C. 552, 556 (1975) (“existence and dissolution [of marriage] is defined by State rather than Federal law”), aff’d, 550 F.2d 1201 (9th Cir. 1977); Von Tersch v. Comm’r of Internal Revenue, 47 T.C. 415 (1975) (same for joint filing). 10 Examples are endless.

10 Indeed, even in the absence of such express incorporation, the well-established rule has been that federal law affords recognition to familial status determinations as governed by the law of the relevant State. As the Supreme Court recognized in DeSylva v. Ballentine, 351 U.S. 570, 580 (1956), “[t]he scope of a federal right is, of course, a federal question, but that does not mean that its content is not to be determined by state, rather than federal law. . . . This is especially true when a statute deals with a familial relationship; there is no federal law of domestic relations, which is primarily a matter 9 See also Lee v. Comm’r of Internal Revenue, 64 T.C. 552, 556 (1975) (“existence and dissolution [of marriage] is defined by State rather than Federal law”), aff’d, 550 F.2d 1201 (9th Cir. 1977); Von Tersch v. Comm’r of Internal Revenue, 47 T.C. 415 (1975) (same for joint filing). 10 Examples are endless.