Bayliss made his first start for Scotland while Sebastian debuted as a second-half substitute, just days after his baby son made his own entrance to the world on Wednesday.
The Welsh-raised prop, who qualifies for Scotland through his own father, missed the birth by preparing for the match but came in for particular praise from head-coach Gregor Townsend after the 29-20 win ended an unforgettable few days.
“It’s been an amazing week,” he admitted. “My partner was pregnant and told me to come.
"Two weeks ago she started [contractions], I went back to see her and to see how things progressed, then we made the decision together to come back into camp last week for me to just concentrate on getting a place in the squad for this game. Then she went into hospital on Tuesday and we got a son on Wednesday."
It has been a whirlwind for Sebastian, and one which doesn’t look like abating anytime soon with rugby and family demands high on the 27-year-old.
This week’s new arrival is Sebastian’s third child, and he also has a step-daughter in his “busy house”. Father-and-son time will be further pushed by Scarlets’ trip to face the Sharks in the United Rugby Championship next week before he can returning to his growing family.
“As soon as we go to Wales, we fly to South Africa on Tuesday which my partner won’t be too pleased about – going from one camp into another one over in South Africa – there’s not much time for her.
"But when I’m back with Scarlets it's just looking to cement a place in the team, they’ve got two quality tight-ends there - WillGriff John and Samson Lee - both international tight-ends so it’s to cement a place in the team really and push on that.
“Previous, I didn't see myself playing international rugby this year. I only came on the scene for Scarlets last year and got a string of games so to come into the international squad is a massive step up and I am going to push on from here. I'm really enjoying it."
There was also third generation pride in the Bayliss family as Josh made his first start for Scotland in the win over Japan after a debut against Australia two weeks ago.
The former England under-20 qualified for Scotland through his grandmother, and Murrayfield appearances were a family privilege said the 24-year-old: “It was a very emotional week for me two weeks ago, when I made my debut, she was very emotional at the game. It was amazing she made it up to see it – without her this wouldn’t be possible.
"I can never take for granted running out at Murrayfield, it’s been absolutely incredible.
"The camp has been incredible for me, I’ve learned so much from all of the players, the back-row, all over the pitch, from the coaching staff, I will look to take that back into club form and try to get us back into a winning run at Bath.”