After the Scanian War, his sister, Princess Ulrike Eleonora of Denmark, married Swedish king Charles XI, whose mother was a stout supporter of the Duke of Holstein-Gottorp. In spite of the family ties, war between the brothers-in-law was close again in 1689, when Charles XI nearly provoked confrontation with Denmark-Norway by his support of the exiled Christian Albert, Duke of Holstein-Gottorp in his claims to Holstein-Gottorp in Schleswig-Holstein.
