Now Playing: Donald Trump Fires Back at Hillary Clinton, Defends Temperament

Now Playing: Donald Trump on Russia, Ukraine, and NATO

Now Playing: Siblings have hilarious reaction after learning their mom is pregnant again

Now Playing: Teen who overcame stutter with Biden’s help takes part in inauguration

Now Playing: Young girls inspired by swearing-in of Vice President Kamala Harris

Now Playing: Kids share their hopes for Biden and Harris

Now Playing: Bidens bring 2 dogs to the White House

Now Playing: Yara Shahidi talks about new season of ‘Grown-ish’

Now Playing: Candace Cameron Bure shares 1st look at new children’s book

Now Playing: Sen. Bernie Sanders becomes unlikely inauguration fashion star

Now Playing: Kamala Harris breaks barriers with her multicultural, blended family

Now Playing: Jill Biden makes history as 1st first lady to hold full-time job

Now Playing: Inaugural poet goes viral after making history at inauguration

Now Playing: Dr. Fauci on rejoining WHO and how Biden’s COVID plan will affect vaccine rollout

Now Playing: Music’s biggest stars give jaw-dropping inauguration performances

Now Playing: COVID-19 vaccine supplies dwindle as Biden takes control

Now Playing: Democrats take control of congress as Harris swears in history-making senators

Now Playing: Biden signs 12 executive actions hours after being sworn in

Now Playing: Biden officially sworn in as president, Harris as 1st woman VP

Now Playing: Complete cuteness overload as this boxer dad looks over his pups