To start having romantic feelings for someone, to fall in love with someone.
fall for (someone)
To create a close(r) relationship (usually with common interests)
bring together
to persuade someone to start having a romantic relationship with you again
win (someone) back OR get back together (with someone)
to receive news from someone else
hear from
To love someone or like someone very much
to care for (someone)
To lose romantic energy over a period of time and eventually slowly come to an end.
fizzle out (UK) / drift apart (US)
to stay together and support each other
stick together
to invite someone to go on a date or to start a relationship with you
ask (someone) out
to take someone on a date
take (someone) out
To support or defend someone when other people don't
stand by (someone)
finish with (UK) / break up (US)
end a romantic relationship
To continue support for someone who is in a difficult situation.
stick by (someone)
to have a romantic relationship with someone
go out with (someone)
To arrange a date for someone with someone else.
set (someone) up
To slowly become less close
drift apart
to share a secret with someone you trust
confide in (someone)