Keep current low interest rate with a new mortgage

[Lj Cal]

Hello,

I want to buy my family home. It would be a direct sale with no brokers involved. The current mortgage interest rate is half of what I was quoted. Is there a way I can take on the current mortgage payments (at the low rate) and get a new mortgage to make up the difference between the existing mortgage and the current value?

For example:

existing mortgage: $50k

current rate: 3%

home value: $200k

new mortgage rate: 6%

Can I take over the $50k at 3%, then get a new mortgage for the remaining $150k at 6%?