Our Leadership

Marnie Matheny - President

My plan after graduating from Texas A&M University in 1990 was to work at Kelsey-Seybold Clinic to earn some money before going on to law school.

Nearly two decades later I'm still with the Kelsey family as president of KelseyCare Advantage and I couldn't be happier leading such a dynamic and caring group of people. I come to work every day feeling lucky to have found a home with such a wonderful company.  Read more...

Dr. Donald Aga - Medical Director

I’m a native Texan and I received my bachelor’s degree in chemistry from Baylor University in 1990.  I then attended the University of Texas-Health Science Center here in Houston, where I also did my residency in internal medicine. As a physician, I have several roles in the medical community.  I’m an assistant professor of internal medicine at the University of Texas-Health Science Center and a clinical instructor of general medicine at Baylor College of Medicine.  But, my primary role is caring for patients at Kelsey-Seybold Clinic, which I’ve been doing since 1997.  As of 2007, I’ve also joined KelseyCare Advantage as the medical director.  Read more...

Theresa Devivar - Vice President of Operations

For me, KelseyCare Advantage is all about taking care of our members. When they call us with a concern or a question, I want them to know how much they matter to us. Everyone on our team knows that the goal is providing absolutely the best service possible.  Read more...

Angela Waltman - Vice President of Sales and Marketing

I became vice president of sales and marketing for KelseyCare Advantage in 2007 after nearly 20 years in health care marketing.  My job is to spread the word about KelseyCare Advantage, which is something I love to do!  When my friends ask what I do for a living, I tell them that I give Medicare beneficiaries true peace of mind.  Read more...

Margaret Drakeley - Director of Compliance & Quality

I was born and raised in Scotland, but moved to Houston in 1990.  I’ve been a registered nurse for nearly three decades and in two countries.  That experience has served me well as director of compliance & quality for KelseyCare Advantage.  Read more...

Denise Martinez Jonathan, Pharm D., R.Ph. - Director of Pharmacy Services

After receiving my Doctorate of Pharmacy degree from the University of Houston College of Pharmacy in 2005, I completed my managed care pharmacy practice residency at Kelsey-Seybold Clinic. I enjoyed the experience at Kelsey-Seybold Clinic, so in 2006 I accepted a position as Pharmacy Administrator of Clinical Services for Kelsey-Seybold Clinic and later, in 2008, became the Director of Pharmacy Services for KelseyCare Advantage.  Read more...