In 567, his elder brother
Charibert I died and his lands of the
Kingdom of Paris were divided between the surviving brothers: Gontrand,
Sigebert I, and
Chilperic I. They shared his realm, agreeing at first to hold
Paris in common. Charibert's widow, Theudechild, proposed a marriage with Gontrand, the eldest remaining brother, though a council convened at
Paris as late as 557 had forbidden such tradition as incestuous. Gontrand decided to house her more safely, though unwillingly, in a monastery in
Arles. In 573, Gontrand was caught in a
civil war with his brother Sigebert I of
Austrasia, and in 575 summoned the aid of their brother Chilperic I of
Soissons. He reversed his allegiance later, due to the character of Chilperic, if we may give him the benefit of the doubt in light of
St. Gregory's commendation, and Chilperic retreated. He thereafter remained an ally of Sigebert, his wife, and his sons until his death. When Sigebert was assassinated later in 575, Chilperic invaded the kingdom, but Gontrand sent his general
Mummolus, who was always Gontrand's greatest weapon, for he was the greatest general in
Gaul at the time, to remove him. Mummolus defeated Chilperic's general
Desiderius and the Neustrian's forces retreated from Austrasia. In 577, Chlothar and Clodomir, his two surviving children, died of
dysentery and he adopted as his son and heir
Childebert II, his nephew, Sigebert's son, whose kingdom he had saved two years prior. However, Childebert did not always prove faithful to his uncle. In 581, Chilperic took many of Gontrand's cities and in 583, he allied with Childebert and attacked Gontrand. This time Gontrand made peace with Chilperic and Childebert retreated. In 584, he returned Childebert's infidelity by invading his land and capturing
Tours and
Poitiers, but he had to leave to attend the
baptism of
Chlothar II, his other nephew, who now ruled in Neustria. Supposed to take place on 4 July, the feast of St.
Martin of Tours, in
Orléans, it did not and Gontrand turned to invade
Septimania. Peace was soon made. '' In 584 or 585, one
Gundowald claimed to be an illegitimate son of
Chlothar I and proclaimed himself king, taking some major cities in southern
Gaul, including
Poitiers and
Toulouse, which belonged to Gontrand. Gontrand marched against him, calling him nothing more than a miller's son named Ballomer. Gundowald fled to
Comminges and Gontrand's army proceeded to besiege the citadel. He could not capture it, but did not need to. Gundowald's followers gave him over and he was executed. In 587,
Fredegund attempted to assassinate him but failed. On 28 November he went to
Trier to conclude a treaty with Childebert;
Brunhilda, his sister-in-law, Sigebert's wife, whose ally he had always been;
Chlodosinda, Childebert's sister;
Faileuba, Childebert's queen;
Magneric,
Bishop of Trier; and Ageric,
Bishop of Verdun. This was called the
Treaty of Andelot and it endured until Gontrand died. Also in 587, Gontrand compelled obedience from
Waroch II, the
Breton ruler of the
Vannetais. He forced the renewal of the oath of 578 in writing and demanded 1,000
solidi in compensation for raiding the
Nantais. In 588, the compensation was not yet paid, as Waroch promised it to both Gontrand and
Chlothar II, who probably had
suzerainty over Vannes. In 589 or 590, Gontrand sent an expedition against Waroch under Beppolem and Ebrachain, mutual enemies. Ebrachain was also enemy of Fredegund, who sent the
Saxons of
Bayeux to aid Waroch. Beppolem fought alone for three days before dying, at which point Waroch tried to flee to the
Channel Islands, but Ebrachain destroyed his ships and forced him to accept a peace, the renewal of the oath, and the surrender of a nephew as a hostage. This was all to no effect. The Bretons maintained their independent mindedness. In 589, Gontrand made a final advance on
Septimania, to no avail. He fought against the barbarians who menaced the kingdom and quelled a rebellion of his niece
Basina at the Holy Cross abbey of Poitiers with the aid of many of his bishops in 590. ==Death and veneration==