In 191 appearances in all competitions between 1999 and 2007, Eustace earned his stripes as a competitive and durable front jumper and will return to Kingsholm to add depth and strength alongside skipper Marco Bortolami, Alex Brown and Will James.
"Gloucester is my home-town club and I am thrilled to be returning," Eustace said. "The year I spent away was hugely beneficial because it allowed me to experience a new culture and increase my understanding of what it takes to compete the top level in Europe.
"To have the opportunity to come back to Kingsholm and press for a first team place in one of the best squads in the Guinness Premiership is a massive challenge but one I am really motivated to achieve. It is great for me and now the hard work really starts."
Young is a highly regarded tight-head prop has and has signed a one-year contract from Leicester. He is the latest addition to Gloucester's growing stable of highly regarded props and will join the likes of Nick Wood and Jack Forster at Kingsholm next season.
In total, he made 13 appearances for Leicester following his senior debut in 2005-06 and has graduated from Murray Mexted's International Rugby Academy and was a key member of Leicester's triumph in the northern conference of the Guinness A League.
"To get an opportunity at a club like Gloucester at this stage of my career is not only very humbling given their history but also a great chance to further my career," Young told www.gloucesterrugby.co.uk
"I would like to thank Leicester for all their help and guidance over the last couple of seasons but the chance to join Gloucester, with their long-term vision for success, outstanding squad of players and training facilities was something I could not refuse.
"They are making it their business to attract some of the best players in the country and I know the hard work starts now for me but I am invigorated by the challenge of it.
"Head coach Dean Ryan made it very clear what he expects and how he wants to achieve success and that was something that really appealed to me - I cannot wait to get started."
The 22-year-old will make the switch to Kingsholm in the summer and head coach Ryan added: "Dave has got the right credentials and attitude to become a very good player and that is what attracted him to us.
"We already have a number of excellent props but it is a position that new, emerging talent can be difficult to get hold of and I that is why we moved quickly to sign him when we learnt he was available.
"We want players under pressure for their places and Dave will add significantly to our front resources, particularly with a guy of Christian Califano's experience retiring."