The duo will join John Chatfeild-Roberts, Peter Lawery and Algy Smith-Maxwell in the team, where they have worked together for the past 11 years.
Sillars will join Jupiter on May 18 to start her new role as fund selection specialist. Most recently, she was the investment director and an executive director at JP Morgan Asset Management.
She has almost 15 years of experience with JP Morgan and its predecessor firm JP Morgan Private Bank and Flemings.
Lewis will join from Jupiter’s private clients and charities division, where he has been an assistant fund manager since February last year, to hold the same role in the Merlin team.
As well as working as a portfolio assistant for the private client team at Jupiter, Lewis was an assistant investment manager at Bestinvest.
Chatfeild-Roberts, the chief investment officer at Jupiter, says: “With the independent funds team now managing over £6 billion in assets, we felt the time was right to expand the team.”