No. Titus Mede II is Prince Attrebus. Prince Attrebus's father is Titus Mede I AND it even said in the books that Prince Attrebus is the next Emperor in the line-up, after Titus Mede I. Thus making Attrebus into Titus Mede II.
Wrong. Titus Mede II is NOT Attrebus Mede. Take this into consideration, the whole Umbriel incident, took place 170 years before Skyrim. Attrebus was already in his 20's, and nearing his 30's by then. He'd have to be 190+ years old in Skyrim, which Humans don't live that long in TES series.
It might be that Attrebus ruled for some period of time after his father Mede I, had a son with Annaig who ruled and the family went through a couple more generations before getting to Titus Mede II.
That's exactly what happened, especially considering the 170 year gap between the Umbriel incident and Skyrim, and the fact that a new family generation usually occurs every 20-25 years.
As to above, look up the Emperor Timeline. Some Emperors lived longer than they should. Their Battlemage prolly did something. Hm?
Yeah, their Battlemages sure did do something alright. Jagar Tharn, the Battlemage of Emperor Uriel Septim VII, trapped Uriel in a magical stasis within a Oblivion plane, and impersonated him as the Imperial Simulacrum. That's the only reason Emperor Uriel Septim VII lived so long.