Honestly, Bilbo will pin this on his Grandfather the Old Took, who wanted to see his favorite grandson happily married off and allowing him to see “dear Belladonna’s great-grandbabby” before he died.
This and perhaps the strain of fairy blood that seemed to appear every now and then in the Took family tree was probably the reason why the Old Took was still hale at his advanced age and strong enough to journey to the restored Kingdom of Erebor where Bilbo was currently staying after his successful quest with thirteen Dwarves. That one of these Dwarves was somebody Bilbo was pining for from afar was something Bilbo certainly wasn’t going to talk about. Honestly, being hit with a classic case of “love at first sight” at his age!
Bilbo preferred to call it “being hit by the Frying Pan of Doom and Having a Severe Case of Arse Over Teakettle Tweenage Twitterpatedness.” He was more than resigned to simply being a Certain Black-haired, Blue-eyed Dwarf as his dearest friend and nothing more, because really, simple gentlehobbit here, certainly nothing worth catching the eye of one specific Dwarf of the Line of Durin.
But of course, Grandfather Took could see right through Bilbo and was thoroughly convinced that Bilbo had “run off to marry a Dwarf” and so the Old Took was determined that his grandson was married “right and proper” and that he’d be able to see his “great-grand dwobbit grandbabby” quite soon.
We must note that Bilbo had to beg nearly all the unmarried members of the Company to help him in his ruse. The younger ones (read: Fili, Kili and Ori) were about the only people Bilbo didn’t consider at all, period, because he felt like the boys were very much like his own nephews and that felt more than a little creepy. The older Dwarves were actually aware of Certain Situations and thus, cleverly and not-so-subtly pushed Bilbo into asking the one person who would not refuse his request.
And so it was that Thorin Oakenshield, King Under the Mountain, found himself under the careful scrutiny of an elderly Hobbit and though, technically speaking, Thorin was older than the Old Took, the Took Patriarch made the Heir of Durin feel very much like a young Dwarfling again. To say nothing of Thorin’s blush when questioned about Dwobbit grandbabies.
We must say that the whole sorry mess was eventually sorted out and Awkward, But Truthful Confessions of Love and Affection were made and Thorin made it clear to Bilbo that he rather liked the idea of snogging him silly. As well as other more interesting things to do in the privacy of one’s bedroom and away from nosy relatives.
The Old Took was delighted to witness the real wedding of his favorite grandson to the King Under the Mountain and did live to see his Dwobbit Grandson, who was named Frodo.