Never ending Love

Sam and Anne are getting married. A new beginning to there 5 year old relationship. Both the families are filled with joy. Both the families went for a dinner with a purpose to know each other better. During the dinner Anne and Sam jokingly asked Sam's father Mark about his love story which he ignored by giving a smile. After the dinner Mark gave Sam a diary and asked him to read it alone. The diary was written by his mom Catherine.
It was the time when she(Catherine) was 18 and about to join one of the best engineering colleges across the globe. She was cute and beautiful. On the first day of the college she met Mark and soon they became great friends. Meanwhile Catherine started falling for Mark and soon she was in love with him. She was about to propose him but was heartbroken when Mark told her that he was in a relationship with Jenny. Hearing this she didn't propose him and thought that it he's happy with her I am happy seeing him like this. 3 years passed
Mark came to know that she was cheating on him and they broke up. She never loved him. Catherine on hearing this immediately went to Mark because he was broken from inside but Mark was do frustrated that when Catherine came she started shouting on her and called her a stupid girl. This hurt her heart and she decided never to talk to him again. They completed their education and went to different nations for job.
5 years later
Catherine was in Australia well settled and enjoying her life when her life turned around again. Mark joined the same company as her new boss. Mark was excited to see her but Catherine didnt forget anything. Mark was talking to her but she kept on ignoring him which made him sad and hurt. One day she came and resigned from her post because she was getting married and was moving to London. When Mark heard this he wanted to cry but he began thinking that why is this happening to me I don't even love her why do I want to cry. He recalled everything and then texted her sorry and asked her if they could be friends. Catherine said to herself why didnt u realised this a little bit before. My life could have changed.
After her marriage, they became friends they used to text and talk to each other for hours. Catherine now even had a 2 year old daughter. Meanwhile Mark was about to come to London because of a business meeting. They both were excited and wanted to see each other. Catherine husband was a scientist and was always busy in his lab so she was usually at home and bored so she had huge time to be with him. After attending his meeting Mark came to meet Catherine and then she took him to show London and it's beautiful places. Meanwhile there were moments when they came close to each other. Catherine was so much in love with him from college days that she couldn't control herself and Mark and Catherine ended up in bed. Catherine realised that she has gone too far and now she has a family so this isn't good. She asked Mark to go away and never return back. After few weeks she came to know that she was pregnant. She didnt wanted abortion but there was no other way. She told everything to her husband to got so furious at this that he asked her to leave his house and they divorced. She again went to US and after the birth of his 2nd child(Sam) she started her job. One day Mark found her and said that Sam was his child also and he wa his father he wanted to be with Catherine and Sam. She refused but when he threatened to go to court to fight for the custody of Sam she agreed. All the three of them started living together and they both were getting attracted towards each other and one day Mark proposed her for marriage. She agreed and was very happy but just days before their marriage she met with an accident in which she died.