Lance Hart, 57, killed Claire Hart, 50, and daughter Charlotte, 19, near the Castle Sports Complex, Spalding, on 19 July.
The women's funeral was held at All Saints Church, in Moulton.
Paying tribute, Mrs Hart's sons Ryan and Luke said she and her daughter had "lived and loved unconditionally".
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Reverend Barbara Hutchinson read the tribute on behalf of Ryan and Luke.
She said: "We were always awestruck that the universe could create something as beautiful as you both.
"We know that right now you will both be looking upon us and wishing us the strength to carry on.
"We owe you everything we have to keep going, to not be defeated.
"With your love, inspiration and determination as an example we have been shown a resilience that cannot be matched.
"We hope to make you as proud as you have made us. We love you Mum. We love you Charlotte."
The funeral was relayed to mourners outside the packed church by loud speaker.
Michael Buble's song 'Home' was played during the service as it was "a song that they both loved".
Speaking after the service Rev Hutchinson said: "It was a very moving service. The tribute that they wrote was very heart-wrenching and I have to say heart-wrenching to read.
"I think [Ryan and Luke] have coped remarkably well. Today, they are both very, very upset and the emotions are very, very high."
At an inquest hearing last month it emerged both women were shot by Mr Hart with a single barrel shotgun.
A full inquest will take place in October.
The family of a mother and daughter who were shot dead outside a leisure centre have paid emotional tributes at their funeral.